Exertional rhabdomyolysis

Dr Richard Godfrey explains what a trainer should know about the potentially serious condition of rhabdomyolysis, which can cause severe muscle pain and long-term damage.

What is it?

Exertional rhabdomyolysis (ER) is defined as rapid skeletal muscle breakdown in response to exercise that stresses muscle beyond its current ability to cope.

Who it affects?

The incidence of ER in a normal or previously sedentary population is not known but, in the US, the incidence among army recruits is around 22 per 100,000 individuals per year<1>, i.e., roughly one in 5,000

There are increased risks of causing exertional rhabdomyolysis if exercising hard with insufficient rest, in a hot environment, and when dehydrated

High-level athletes are at risk after a lay-off, whether initiated by injury, illness or simply requiring a rest or a break at the end of the season

Creatine kinase

Damage caused by exercise can lead to an increase in the concentration of the enzyme creatine kinase (CK). With hard training, most normal, healthy individuals will have values of CK elevated to between 500 and 5,000 IU/L and normal resting levels tend to be 60 to 174 IU/L. With more severe muscle damage and breakdown, blood CK can be greater than 10,000 IU/L<2> and can include the appearance of large protein molecules in the general circulation. The most significant of these is myoglobin, which is unfortunately large enough to present problems for the kidneys in filtering it from the blood. As a consequence, it can cause tubular obstruction, disruption of function, acute kidney injury, and can result in renal failure – a potentially life-threatening condition. Don’t ignore the symptoms!

Symptoms

Persistent muscle pain and dark tea-coloured or cola-coloured urine

Vomiting, confusion, swelling of the affected area

Flu-like symptoms

Complications

Cholesterol-lowering agents such as statins (the most widely prescribed drug in the world<2>) can negatively affect production of adenosine triphosphate (ATP) by mitochondria and this also leads to muscle damage.<3> On the one hand, it is encouraging to know that statin users are likely to adapt just as well to the exercise stimulus but, on the other, it is sobering to know they are at greater risk of ER.<4> So, one must be quite wary when having a middle-aged statin user exercise hard in the heat when dehydrated.

Prevention

It is recommended that the first session with a new exerciser should be used to both assess the current conditioned state (‘fitness’) as well as to act as a ‘pre-conditioning’ session. The same applies to highly conditioned athletes who have had a break of 10 days or more.

A common underlying feature of ER is exercises with a large eccentric component.<5> So, the first session could be a resistance training session in the gym, but should be an easy one with perhaps just one set per exercise. The second session can then address the ‘overload’ principle, that is, doing a little more than the individual is currently accustomed to.

Throughout the session, ensure clients are well-hydrated pre, during, and after an exercise session.

About the author

Dr Richard Godfrey is former chief physiologist of the British Olympic Medical Centre, and now senior lecturer in physiology and sport and exercise science at Brunel University, London.